The brain sciences may reduce retributivist punishment (based on moral blame) and increase the role of consequentialist punishment (aimed at rehabilitation/reintegration, or failing that, incapacitation and public protection). It is not clear that this would be a progressive or humane response. CS Lewis' great essay illustrates the dangers of the rehabilitative approach: C.S. Lewis, “The Humanitarian Theory of Punishment” (December 1995) Washington State Bar News 15.

The law traditionally looks at capacity in determining blameworthiness. The NCRMD (not criminally responsible by reason of mental disorder) test focuses on certain mental capacities: the ability to understand one's actions and the ability to appreciate the moral wrongness of one's actions.

Should the NCRMD test incorporate other mental capacities such as adequate emotional circuitry and executive control? In other words, should psychopaths be regarded as "emotionally disabled" and those with impulsivity problems be regarded as "self-control disabled" to an extent that excludes or reduces moral blameworthiness?

We have multiple reasons to avoid criminal behaviour - internal emotional inhibitions against harming others as well as the deterrent impact of the threat of punishment. If a psychopath is "emotionally disabled," does it make sense to exonerate him/her as morally blameless? Wouldn't that just remove the one remaining reason to refrain from offending? In fact, perhaps psychopaths are better able to respond to deterrent threats than others because they are primarily self-interested and more likely to be able to calculate coolly than others.

The psychology of punishment and judging moral blameworthiness

One intriguing possibility is that rational judgments about free will and capacity do not drive our decisions about blame and punishment, and instead emotional or psychological. In other words, the emotional need to blame and punish causes us to believe in free will and to find people capable. Similarly, in a society in which prisons are the main mechanism to control or reduce perceived risk to the public, the knowledge that prisons are very unpleasant punitive places may cause us to "need" to see offenders as bad in order to sent them there.

To what extent can the criminal justice system diverge from public intuitions about moral responsibility and blameworthiness? One of the functions of a state-sponsored system of criminal justice is to exercise a monopoly on retributive violence and so to discourage vigilantism. If a non-retributive system does not answer these emotional needs, it will be necessary to address them in some other way - perhaps by public education about the biological and environmental factors that lead to offending behaviour.

Impact of biological accounts of mental states and behaviour on offenders

While we have been looking at the impact of biological explanations on judges and on society, other possible recipients of these messages are offenders themselves. What might be the effects on identity, self-control, and behaviour of these biological explanations of behaviour and mental states? Will they reduce the sense of agency and responsibility? Does criminality become a self-fulfilling prophecy in these circumstances?

Perhaps there is utility to maintaining the idea of free will because it is socially useful. There is experimental evidence that people primed with the idea that behaviour is determined (i.e. they lack free will) are more likely to behave antisocially (cheat others, reduced willingness to assist others etc.).

The "double-edged" sword of biological explanations

The group was polled to see who would regard a biological explanation of psychopathy as a (a) mitigating factor that reduces sentence (due to reduced blame), (b) aggravating factor that increases sentence (due to risk). Most recognized an impact of both at the same time.

Chandler found evidence of both effects in her study of neuroscientific evidence in Canadian criminal cases. Judges are likely less willing to accept a mitigating impact on blame in more serious cases. This is because they flip into consequentialist reasoning where the perceived need to protect society is higher.